1. Field of the Invention
The present invention relates to a flip chip light-emitting diode package. More particularly, the present invention relates to a flip chip light-emitting diode package capable of preventing damage from electrostatic discharge, promoting emission efficiency and thermal dissipation characteristics to increase lifetime.
2. Description of Related Art
In recent years, III–V nitride semiconductor materials have been utilized to fabricate high-temperature devices and opto-electronic devices capable of emitting light in the blue to ultraviolet wavelength range. In particular, nitride based compounds semiconductor that contains group III–V elements including GaN, GaAlN and InGaN have been used to fabricate various types of light-emitting diodes.
FIG. 1A is an equivalent circuit diagram of a conventional flip chip light-emitting diode package. To prevent any electrostatic discharge (ESD) from damaging the light-emitting diode structure 30, the light-emitting diode 30 is connected in parallel with a Zener diode 40. The Zener diode 40 is always being turned on because the Zener diode 40 operates at a breakdown region. When a forward bias voltage is applied to the two terminals V+ and V− of the light-emitting diode 30, carriers in the P-N junction of the light-emitting diode 30 generate a forward current leading to the emission of light. However, if an abnormal voltage or static charge is applied to the light-emitting diode 30, excess voltage will discharge through the Zener diode 40 operating at the breakdown region. The discharge current passes through the Zener diode 40 instead of the light-emitting diode 30 so that the light-emitting diode 30 is protected against irreversible damage due to an abnormal voltage or large static electricity discharge.
FIG. 1B is a schematic cross-sectional view of a conventional flip chip light-emitting diode package. As shown in FIG. 1B, a transparent substrate 32, an N-doped GaN layer 34, a P-doped GaN layer 36 and electrodes 38a, 38b together form the group III–V GaN light-emitting diode 30 in FIG. 1A and an N-doped silicon 42, a P-doped silicon 44 and metallic layers 46a, 46b together form the Zener diode 40 in FIG. 1A. The bumps 50a and 50b shown in FIG. 1B are made from a solder material. Through the bumps 50a and 50b, the P-doped silicon 44 is electrically coupled to the N-doped GaN layer 34 and the N-doped silicon 42 is electrically coupled to the P-doped GaN layer 36 so that an equivalent circuit as shown in FIG. 1A is formed.
In a normal operation, a forward bias voltage is applied to the V+ and V− terminal of the flip chip light-emitting diode 30 so that a current flows from the P-doped GaN layer 36 to the N-doped GaN layer 34 to produce light. The light so generated extracts from the transparent substrate 32. When an abnormal voltage or static charge is applied to the terminals V+ and V−, the excess voltage causes a discharge current through the N-doped silicon 42 to the P-doped silicon 44 without passing through the light-emitting diode 30.
Although the aforementioned structure protects the light-emitting diode against ESD, additional processes are required to form the P-doped silicon 44 within the N-doped silicon 42. The most common technique of forming the P-doped silicon 44 within the N-doped silicon 42 includes an ion implantation method. The ion implantation method is capable of forming a doped region having a given depth more accurately than a conventional diffusion method. However, forming the P-doped silicon 44 within the flip chip light-emitting diode package demands an accurate control of the dosage as well as energy through the ion accelerator of an ion implant equipment. Hence, expensive equipment (ion implant equipment and accessory gas supply system and vacuum system) must be purchased and a lot of time must be spent to produce a package with this structure.